A federal judge knocked down Tuesday a Navy plan to deploy submarine- hunting sonar in most of the world's oceans, saying the devices endanger entire populations of whales, porpoises and fish.

Magistrate Judge Elizabeth Laporte of the U.S. District Court in San Francisco said a permanent injunction should be issued that will bar the Navy from using sonar in areas including 14 million square miles, or about 40 percent, of the Pacific Ocean.

But she left open the possibility of limited use of new low-frequency active sonar technology for testing and training in certain areas not considered rich in sea life. Also, Congress is considering legislation that would effectively allow wider use of the sonar technology, despite the judge's ruling.

The ruling caps a decade of legal battles between the Navy and environmental groups concerned about the damaging effects of sonar, particularly to the brains and navigation systems of whales and other marine mammals.

The Navy's sonar plan doesn't comply with three federal statutes, Laporte found, citing provisions in the Marine Mammal Protection Act, Endangered Species Act and National Environmental Policy Act "designed to protect the oceanic environment and safeguard the whales, dolphins and other marine life within it."

The environmental groups, in their arguments, proved the "likelihood of irreparable harm," Laporte said.

"Balancing the harms and weighing the public interest, the court concludes that it should issue a permanent injunction, but that it should not impose the complete ban on peacetime use of (sonar)," the judge said.

Rather, the injunction should be "carefully tailored to reduce the risk to marine mammals and endangered species by restricting the sonar's use in areas that are particularly rich in marine life, while still allowing the Navy to use this technology for testing and training in a variety of oceanic conditions," Laporte said.

OCT. 7 MEETING

The judge ordered the parties to meet to negotiate possible terms of the permanent injunction, and scheduled a conference for Oct. 7.

The environmental groups had argued that the high decibel levels of the sonar, or underwater radar, could disrupt migrations, damage whales' hearing and cause hemorrhages in the brains of sea animals. They blame sonar on mass strandings in the Bahamas in 2000 and the Canary Islands last year.

Andrew Wetzler, a defense council attorney, called the ruling "a major victory for the oceans and for all people who want to preserve them." Yet, he cautioned that this week Congress is considering versions of a Defense Department budget that offer exemptions to the military in the oceans.

"The court held today that the Marine Mammal Protection Act requires a showing that there would be a take of only a small number of animals. That would be completely eliminated" under the proposed language, Wetzler said.

"It's sad. Instead of heeding the judge's message, the Bush administration has gone to Congress for blanket exemptions to undermine today's decision," he said.

Rebecca Lent, a spokeswoman for the National Marine Fisheries Service, said her agency doesn't oppose the proposed legislative changes sought by the military because the mammals are protected by other legal provisions.

Lent said Tuesday's decision recognizes the need to safeguard interests on both sides. Yet, she said, "The judge sent a clear signal that she's looking for wider margins of safeguards" for sea life.

According to the ruling, the agency will have to improve its plan by extending a coastal buffer zone so that it would include more of the continental shelf, avoiding more of the deep open ocean during times when marine mammals and other endangered species may be present in significant numbers. Also, additional analyses must be conducted to plan Navy vessel routes to minimize exposure to the mammals, Lent said.

In a statement, the Navy said that it was reviewing the decision, and that it had already spent more than $10 million for a two-year peer-reviewed research program on impacts of sonar.

The sonar "will greatly improve the Navy's ability to detect and track quiet diesel submarines, which present an increasing threat to U.S. and allied forces operating in areas of strategic interest," the Navy said.

SONAR PLAN

The Navy wants to use two sonar ships. From each ship, an array of 18 loudspeakers, each the size of a Volkswagen, would be suspended in the ocean at a depth of about 200 feet.

Each ship's array operates at a frequency range of 250 to 500 hertz and emits sound at 215 decibels. When the sound strikes an object, echoes return and get picked up by a couple of hundred underwater microphones. The readings can be used to determine the location of a submarine and how fast it's moving.

According to the plan, the Navy had to show that it would prevent harm to marine mammals and sea turtles by keeping them away from the sonar ships, which at close range produce high decibel levels.

Sounds in the deep ocean can injure the ears and cause internal hemorrhaging in marine mammals as well as interfere with communication, breeding, feeding and migrations, according to the Woods Hole Oceanographic Institute.